Multicellular fractionation column and the like



A. K. BREWER 2 Sheets-Sheet 2 Filed May 13, 1949 Ill/"l" awe/11M ATTORN EY\$ Patented Dec. 15, 1953 MULTICELLULAR' FRACTIONATJQN COLUMN AND THE LIKE Aubrey, KeithBrew ashington, .D. C-

. pplicationMay 13, 1949, Serial No. 93,152

This invention relates to an apparatus and method for effecting improvements in the art of gas and liquid contact and aims generally to improve the same. The invention is well exemplified by its application to distillation bysubjecting a flowing film of liquid to high turbulence contact with a counter-flowing stream of vapor in such a manner that high throughputis obtained in a fractionation column having aremarkably low HETP. HETP is defined as the height of an equivalent theoretical plate; i. e., the length of column required to produce a change in concentration equivalent to one theoretical plate.

Prior to this invention it has been shown, (Willingham, Sedlac, Rossini and Westhaver, Ind. and Eng. Chem, vol.'39, page 706, year 1947) that the efficiency of a fractionation column is markedly increased by induced tubulence inthe vapor stream. Means and methods for applying this effect have been limited'to anapparatus consisting of a cylinder spinning in a tube in which the spacing isa few hundredths of aninch. As a consequence, while very low'HEPT has been obtained the throughput is too low to meet most commercial objectives.

Some of the objects of the present invention,

severally and interdependently, are: To achieve intimate turbulent contact between a gas anda liquid, for example a flowing film of liquid and its vapor, in uniform distribution andcomposi tion in a given plane across a column of wide cross-sectional area to achieve countercurrent contact between a liquid phase distributed as a flowing film over a plurality of "surfaces and a gas phase in a high state of induced turbulencewhile confined within walls closely spaced at right angles to the direction of flow, and the whole being regularly distributed as to composition across any given cross-section of confining col.- umn; to obtain exchange between liquid and gas or vapor in a fractionation column or the like in a very short length of column whiletransporting relatively large masses of material; to obtain relatively large transports of material through.

28 Claims. (01. Mil-83) 2 paratus herein disclosed for carrying it out. The invention resides in the novel method and subcombinations thereof herein described and claimed, and in the novel features, arrangements and combinat'ionsof apparatus for performing the method herein disclosed and claimed.

It has long been known that the efficiency of a fractionation column, as defined by the throughput divided by the is limited by the rate of exchange between the ascending stream of vapor and the descending stream of liquid. This exchange is in reality the result of the evaporation of a certain amount of liquid from a givensurface and the simultaneous condensation of anequivalent amount of vapor.

The factors determining the quantity of liquid evaporated for .efiective exchange in unit length of column are the extent of surface exposure per volume of liquid involved, the time as determined by the rate of liquid descent, and the absenceof surface depletion; i. e., reduction'of the'concentration of the evaporating fraction exhibited in the exposed surface of the liquid as occurs in stagnated liquids.

The factors determining the rate of vapor condensation on the liquid surface are all dependent on and limited by and directly proportional to the number of times the average vapor molecule will strike the liquid surface while traveling through a unit length of the column. This number is a direct function-of the area of liquid exposed and of the turbulence in the vapor phase; it is an inverse function of the distance a molecule must diffuse through'the vapor to strike the liquid surface; i. e., the-thickness of the vapor volume, and of the velocity of vapor travel.

It must be borne in mind that under full countercurrent reflux a quantity of material passes as liquid down the column which is the same as that which passes as vapor up the col-- umn. In productive fractlonating operations when :an output is being withdrawn atthe top, the quantity of "liquid running down is equal to the vapor transport less theoutput.

Two major factors "must be considered in augmenting the rate of exchange between liqui and vapor and hence reducing the HETP of the column. They are ('1) theprovision of a method and constructionproviding extreme thinness and nce' n hth q id and vapor st ms, a d 2' he provi ion of such acmethodvand contruc i n n wh ch channeling is eliminated j st as far as possible.

vBy channeling is meant th pa age of eith r liquid or vapor through a section of the column without undergoing exchange. It may take the following forms: (1) A non-exchanging throughpassage of vapor upwardly at some point; (2) a blowback of liquid mist in the ascending vapor;

(3) rivulets of liquid running down. All the above will give rise to non-uniformity of distribution of liquid and vapor across the column at some point.

In the present invention a high rate of liquidvapor exchange is induced while channeling has been almost completely eliminated. The construction of an exemplary column operating in accordance with my new method for obtaining these ends is shown in the accompanying drawings, in which:

Fig. 1 is a schematic drawing of an entire fractionation column assembly embodying the invention.

Fig. 2 is a diagrammatic plan view of a spiral brush employable therein.

Fig. 3 is a detail in vertical section of portions of the same.

Fig. 4 is a detail in plan of a portion of another form of brush element.

Fig. 5 is a detail in vertical section of a portion of the latter.

As above noted the present invention provides a unique method of contacting a descending liquid with a gaseous or vaporous medium in a plurality of stages, as well as a simple and efficient apparatus for practicing the method.

In effect, in the herein-disclosed method, the liquid is distributed in each stage in the form of a reticulated film-formed mobile structure comprising upper and lower apertured films and downfiow or transfer films bridging therebetween. The downfiow films are positively moved about between, and in contact with, the upper and lower apertured films in each stage. They thus draw liquid from different parts of the upper film successively' and deliver liquid to different parts of the lower film, successively. The liquid is therefore being continuously mixed or cross-mixed, but without bulking, and its composition at any given level in the stages is maintained substantially uniform. The positive movements imparted to the films and the transfers of liquid between relatively moving films, as also the motion imparted to the liquids in the films, prevents stagnation therein and mere local impoverishment or enrichment of the film surfaces. The gaseous phases in each stage are also positively moved about in contact with the films in that stage, and the motion imparted thereto aids in creating gas turbulence and in preventing gas channeling. The gaseous phases are also preferably expanded transversely into each stage, which assists this action.

In the preferred embodiments herein disclosed the descending liquid is passed to the upper apertured film of each stage from the lower apertured film of an overlying stage through tubular films bounding the apertures therein, this step being so performed that bridging of the apertures, and consequent blow-back of liquid, is avoided. The gaseous medium is preferably passed into and out of the reticulated filmformed structure of each stage by way of the free-flow passages within the last-named tubular films. The gas is thus maintained in contact with downfiowing liquid in film form even during its transfer from stage to stage, as well as being expanded laterally on its entrance into each stage.

In addition, in the preferred embodiments of the method, the liquid in the respective films, and especially that in the apertured upper and lower films of each cell, is positively smoothed and spread and prevented from accumulating into globules or drops, and this smoothing or spreading operation further aids in promoting uniformity of composition in each of said films and in preventing mere surface impoverishment or enrichment thereof.

In the embodiment shown in Fig. 1 the invention is applied to a fractionating column. This column comprises a pot I and a column casing 2 extending upwardly therefrom. As best shown in Figs. 2 and 3, this column 2 is divided into superposed cells 3 by mutually spaced plates 4 which are provided with regularly spaced openings 5 of a size not bridged by the liquid to be processed. The upper end of the column is provided with a vapor dome 6, which is diagrammatically shown as connected to a condenser l by a vapor outlet 1a. The condensate from condenser 1 may be returned to the column through a distributor 8, which may be mounted on a rotating shaft 10. A movable distributing means or rotary brush 9 is juxtaposed to the uppermost of the plates 4 and spreads the liquid thereover. Similar distributing means or brushes II are juxtaposed to the top and bottom surfaces of each of the cells 3, and afford moving turbulizing and spreading surfaces therein.

The brushes 9 and. l I, which may be of any suitable construction, although the forms hereinafter exemplified are preferred, are mounted on the shaft l0, which rotates in thrust and aligning bearings l2 and 13. These may be suitably associated with the casing as by the lower spider l4 and the bearing cap or support IS. The bearings may be mounted internally of the casing, when this is desired, as exemplified by bearing l2 herein, or externally, as illustrated in connection with bearing [3. Where external mounting is employed, the shaft I0 is packed where it passes through the casing, as indicated by packing gland [6 carried by casing closure plate 2a.

The pot I, in the form shown, is connected with a boiler l1, and is bolted or otherwise tightly assembled to the casing 2, as indicated at l9. The internal elements of the column, comprising the spider [4, plates 6, plate spacers I8 and pressure ring 20, together with the rotor and. shaft assembly interassociated therewith, is supported in the form shown by a removable retaining ring 2| secured to the lower end of easing 2. A jack ring I2 secured to the upper end of easing 2 in the form shown, provided with suitable jack screws or the like, serves to tightly clamp the assembly of plates 4, spacers i8 and. pressure ring 20, retaining the plates 4 in predetermined spaced relation and effectively sealing the peripheral regions thereof against channeling. The rotor assembly and its thrust bearing i2 may be verticallv adjusted. in the form shown, for centering the brushes II in the cells 3 between plates 4. as by adiusting collars 24 and 25 and bearing lift screws 26. The shaft It] may be rotated in any suitable way; for example, by a power drive comprising a belt pulley 21.

The apparatus preferably comprises a liquid distributor 8. This distributor, as shown in Fig. 1, may comprise an annular trough provided with transversely extending generally radially arranged perforated spray pipes shown at the under side of the trough, and may be fed through the return pipe 3| from condenser 1. A condenamass sate draw-off valve 32 is associated withsthis-line, and feed and'draw-ofi valves 33 and -31 are associated with the boilerand pot circuit.

With-the arrangement shown; the'entirezassembly' of plates 4, rings .llshaft :10, brushes 9 and J1, and associated parts may be removed through either end of the casing 2 merely by disconnecting the pot or-vapor dome,and the parts associated therewith. The forms-cf pot and dome shown aresuitablefonmoderate pressure operation, but would of course be modified in accordance with welleknown principles for operation at extremely high or extremely low pressures.

The brush or turbulizer and: spreader element, in Figs. .1 to 3, comprises a hub section 1411, splined or otherwise secured :to' the shaft 110. This .hub section has threaded or otherwise secured to it radial arms I lb, and the brush proper comprises a spaced spiral element or sweep means :Hc suitably supported by the arms 'Hb. In thisform thersupport is afforded by inserting the arms or rods I-lb through aligned holes in thevconvolutions of the spiral strip and through spacer washers lid interposed between them, througha lock .nutand washer He and into the threaded holes in the .hub Ha. Ahead :orretainer cap Hf shown as demountably secured to the outer end of each radial arm wll provides, with the nut 1 le; for tight clamping of the brush convolutions in each instance. The height of thesp'n'al'sweep "I h: is preferably-such as'to just clear the surfaces of "the apertured plates 4., which are positioned relative to it by spacers l8, hereinafter described.

In the form shown inFigs. 4 and 5, the spreader and'turbulizer comprises a tubular grid H7, -ca-r ried by the huh I .171: and similarly'related to the plates '4. This entire assembly can be castusing any rigid :material such as castalloy. Therdimension of the openings 23 :may vary between one-eighth of an inch :and about one-half of .an inch depending on .the rotor thickness.

The plates 4 and hubs 11a and .I lit, as shown, are preferably formed to prevent channelling past the inner edges of plates, herein by housing such inner .edges in peripheral hub channels, indicated at Hm. These channels, in the form shown, particularly when operating on lubricant stock, may help maintain alignment of the parts even though all the desirable adjustments thereof hereinafter described may not be'perfectly made.

Other forms of brush element may also be employed, so long asth'ey are capableof transferring liquid from the upper to the lower'plate of acel-l. in filmwise fashion spread out over an expanse of surface, and are capable of inducing turbulence in the ascending vapors.

In operation of the fractionating column of Fig. 1 in accordance with the method of the present invention, the liquid to be fractionated is boiled in pot I. Thevapor passes upward through column 2. hits passage through "the column 2, the vapor must-pass through the series of cells J 3 formed by the uniformly spaced plates 4. The vapor that emerges from the topmost plate enters chamber I5 at the topof the column and then passes on to condenser l, where it is condensed and returned to the column through distributor 8. The liquid, "upon flowing out of the openings of distributor 8, is spread filmwise over the upper surface of top plate 4 by rotating brush 9 splined'or otherwise fastened to shaft I0. The liquid passes downwardly in tubular film form along the walls of openings 5 in plated 6 to the finder-smothered. Here his :contacted by brush JJI also fastened to shaft 10 and is brushed outer spreadasxaithinifilm brush 1:] and on the underside ofthecvcrly-in platen. The liquid so spread filmwise brush H flows downwardly on the. brush sinfacespbeing spread out thereon 'bythe rotary motion thereof. and :is delivered by ravity to the lower edge :of the brushywhere it is spread upon the top or the plate I underlying thebrush 1:1 and forminsthe lower wail of thetopmost cell 13. The liquid thus flowsdown int-ubularform throughthe openin s 5 .in:.all the plates 4 and is spread on the surfaces thereof and of the brushes-progressively until it is returnedtoipot l. The Iliquidisthus spread out in the form of wide area. descending films in each cell due to the operation of rthe'prnsh with-a consequent low Thus. liquidrfiow ing through "the open-ingsi'inxplates 4 is swept alon the bottom-surface :cf the plate Sbyitherotatingbrush H in theform'of'iathinfilm. As

this-film builds up it is carried olf the undersurface'of the plate by the .brushand aliowed'to rundown and spread over the brush sinfaces and isdeposited witha sweepingmotionpncthe top :surface of the nex-trlower plate of theisame cell. The spinal strip form "of-rotarybmsh is especially advantageous in "this connection. :By it the liquid is spread radially and arcnmtely along :the plates 4 and-is spread :centrif-ugallyzand by wall displacementralong the surfaces Dfithe spiral. Thus liquid from one opening 5.10! the plate 4 is especially well .intermixcdwztth'iliquid from the other openings ofthe same ,plateito provide a uniform compositionend:distributionnver the surfaces of each :plate. The-liquid "in teach cell .is thus distributed in the form of 1a thinfilm over the bottom surfaceof one plate; over the brush :-surfaces, and over "the topsurface of :the plate next (below. Since :the i-plates are flat and the clearance between the brushes and plates small. at no point is the fllmthickness permitted tobuild-up to form pools.

Channeling theentrainment of :liquidiinoplets 1n the upward-moving vapor zstrcami is delimmeted by the rotation ofthe brushes which sweep the vapor free of droplets. Blow-.backand spraying-ofliauidin-the openings .5 isavciidedsmce the liquid does not-bridge over these-openings. Thus by the-wiping-andispreading method of this invention the liquid-is conditioned for rapid exchangev by being spread over the :entire area of film-supporting surface'in'cach :cellas a'flowing filmwith oontinuouscross mixing and surface renewal.

zThe v p ilq ns p through opening 5 in plate 4 s conditioned vfor rapid :cxchange iby'xinduced high turbulence andrby close wall spacings. High turbulence is insured by wexpansion: of the vaporinpassinsthr ue th beningszfiiintozcells 3 where-the cross-sectional-freespa e is'inoreased several .fold. The turbulence so inducediisseyeral times that obtained whenrnoeexpansion and: contractioniin the" vapor is involved. High turbulence in :the vapor stream is also induced I by the rotation of brushes H. "'I'heclose-spacing of the elements-of the brus'hes *1 i also insures rapid exchange by reducing the thickness of "the vapor streams passing 'throughfthem. Relatively ,slow.

S upward vapor velocities are provided by the large cross-sectional free space of the column.

The dimensional limits of the column are not critical. Nevertheless a number of limits can be prescribed to insure optimum operating efliciency and to prevent constructional difficulties. Thus, the diameter of the column should preferably not be more than three feet with about four feet as an outer limit. A minimum diameter of two inches would appear to be near the lower limit. The diameter of column selected is to be determined by the output desired. The cell spacings as defined by the distance between successive plates should preferably be within the range of three-eighths of an inch to two inches depending on the diameter of the column and the operation performed. The thickness of the Plates is important only in that it should be sufficient to maintain rigidity and prevent sagging.

The openings in the plates should be sufficient to prevent vapor block by films of liquid forming across the perforations. Diameters ranging between one-eighth of an inch to one-fourth of an inch are satisfactory for most petroleum operation. The spacings in the brushes, whatever their type, should be free but relatively small to provide a short diffusion distance for the upwardmoving gases, but should be sufficiently large to prevent liquid block in the openings. A maximum of surface is desirable. In consequence the spacings would usually not be smaller than oneeighth of an inch, or larger than one-half of an inch at the point of minimum diameter, in operating on fluids of normal viscosity and surface tension.

The speed of rotation of the brushes is not unduly critical. In operations in which mist is formed, the speed preferably is sufficient to insure that the mist particles will be struck by a moving wall, or displaced thereby, before they can pass completely through a cell; preferably this rate will be so correlated with the rate of rise of the gaseous phase, and the height of the cell, that the mist particles are, for the most part, intercepted by a brush in the lower third of the height of a cell. For most purpose brush rotation at speeds of the order of one hundred to two thousand revolutions per minutes will be found satisfactory, depending on the operation performed and the physical characteristics of the apparatus.

The direction of rotation, particularly in the case of spiral brushes rotated at relatively high speeds, is preferably such that they tend to wipe or scoop the liquids and gases toward the hub of the brush, counter to the centrifugal forces tending to advance them toward the outer periphery. This would mean a clockwise rotation of the brush H relative to the plates, as viewed in Fig. 2. In this way channeling adjacent the spacer members I8 is avoided, and uniformity of conditions throughout the cell is fostered.

Rather close tolerances in constructional dimensions are preferred, to provide interchangeability of the brushes for the various cells. Also the column casing 2 is preferably smooth and of uniform bore to provide for easy insertion and withdrawal of the plate and rotor system from either the top or the bottom as illustrated in Fig. 1. Furthermore the plates 4 are preferably substantially fiat to prevent the formation of pools and to provide a smooth surface over which the liquid film is readily spread, and the rings l8 spacing the plates 4 within the column 2 are preferably made with such accuracy that all cells are of equal size, and to prevent channeling of liquid between the rings and the column walls.

The rotating shaft must be large enough to be rigid. The rotating brushes may be attached by splining, keying, use of set screws or otherwise. A hexagonal or fiat-sided shaft is permissible. It may be desirable to insert bearings at points along the column to prevent whip. This is accomplished by means of arms, or more easily by use at such points of heavy plates generally similar to plate 4, adapted for the carrying of bearings.

Tapered roller and ball bearings (l2, I3) are preferably used for the rotating shaft to insure alignment. Lubrication is not necessary for internal bearings such as bearing l2 when it is provided by the liquid itself. All internal elements are preferably of non-corrosive material such as stainless steel and Monel metal to permit ready assembly and disassembly.

The advantages to be gained by the present invention are numerous compared to' conventional packed columns and bubble towers.

The efiiciency, as defined by the throughput divided by the HETP, is very high. The throughput can be made large since the crosssectional free space is larger than is possible in any packed column and channeling is negligible. The HETP is low due to the large liquid film area, the high turbulence in the vapor stream, and the short diffusion distances. A single cell represents up to 0.75 of a theoretical plate under full counter-current reflux; this is equivalent to an HETP of from one to two inches. At maximum output the I-IETP never exceeds three to eight inches. This is to be compared to three to five feet for large bubble towers. As a result processes which have required a one-hundred foot to a one-hundred-andiifty foot tower can be accomplished with a ten to twelve foot column employing the present invention. This means that high efliciency fractionation columns can be housed, placed under ground, or employed on shipboard. This is of importance as a protection against wartime and weather hazards. A mobile refinery is also of economic importance since it will often prevent reshipment of oil. To illustrate, crude from remote fields is now shipped to this country to be refined and then returned to the remote areas as aviation gasoline and refined products.

Other advantages of the present invention will be readily apparent. Among these may be mentioned: (l) The pressure head across the column is negligible since the cross-sectional free space is large with no tortuous gas passages and since no hydrostatic head must be overcome. This means that the column can operate at low pressures, even below one millimeter of mercury. Thus a large number of unstable compounds which. crack in ordinary fractionation columns can be fractionated at reduced pressures. Mercaptans and vitamins, for example, are of this nature. (2) The rigid and tubular construction made possible by this invention permits operation at high pressures. The advantage of this to the natural gas industry is apparent where distillations at one thousand pounds per square inch or more are of economic value. (3) A column constructed to employ the method of this invention is very small for its capacity. It thus can be encased in a thermal jacket to permit operation at any desired temperature, both elevated and reduced, even down to liquid air temperatures. Thus mixtures of low boiling compounds can be separated with ease and in quantity. (4) The invention pro vides extremely low hold-up of liquid. Thus the column comes to equilibrium within a few minp ecewise utes or hours even-for the "largest "sizes. Since the hold=up "is "of the order of one twenty-fifth '-to' one-fiftieth of that for bubble'tow'ers 0f substantially equal'capacity, the equilibrium "time is proportionally shorter. -nlsosmall quantities fo'f material can be fractionated and "only negligible amounts "are left uniractionated. This is important in the case "of high cost materials.

(5) The column is adapted to the separation of isotopes. --Its high'platage 'andlow hold-up make it ideal for the concentration *ofisotopes by two methods: First, by fractionation, for (example, separation of heavy oxygen by thepounter-ciurent fractional distillation'oiwater; and second,

the distillation or reaction of acids and 'c'orro- I sive substances. ('8) The apparatus is easily cleaned. In usual sizes, the entire cell system is -removable in an -hours time for cleaning and repairs. (9) The apparatusiis.readilytransportable. Conventional one hundred to .0118 hundred fifty foot bubble towers "are so .diificu't to ship that their installation at remote points 'frequently is .not practical. The present "column can be transp'ortedeas'ily by .anylighttruck.

From the foregoing description of exemplifying embodiments it will be apparent that the present invention :provides a new [and useful method'and apparatus 'foraffec'tinggas and liquid contactwhi'c'h is :notlimite'd to the particular details 'of the embodiments herein described. Itis therefore to be understood that the exemplary embodiments 'hereinset forth are'illu'strative and not restrictive of the invention, the scope of which is. de'fined in the appended claims. All modifications which .come within themeaning and range of equivalency of the claims are therefore intended to be included therein.

I claim as my invention:

1. A method of contacting :a descending -liquid with a gaseous =or vaporous medium which 'consists in distributing the liquid :in the form ct :a reticulated film-formed mobile structure icomprising spaced apart upper :and lower apertured surface supported films and surface supported downfiow films bridging therebetween; positive- 1y laterally transporting said :surface sup-ported downfiow films about, between and in edge 'contact with said upper and lower apertured films; passing liquid to said npperfilm through surface supported tubular films :bounding the apertures therein; lpassing liquid :tromsaid lower film through surface supported tubular filxns :bou-nding the :apertures :therein; and ifiowing the gaseous .rnedium :into and but of said reticulated filmformed structure by way or the tree-flew passages provided .-'by said tubular films ito Eb'e positively laterally :movedsabout withitheilaterally transported films between the films of saidfilmformed structure for promoting intimate itur bulent surface contact rof the with the :suritace supported liquid films thereof.

2. a method or contactingia descendmgiliquid with a gaseous or vaporous me'dium'in-a plurality of stages which consists in distributing the liquid in each stage in the form 0! a reticulated film Tormed'mobfl'estructure' compnslngsDacedapart therein; passing liquid 'from said lower filrn tfo ahunderlyln'g stage through surface supported tubular films bounding the apertures "therein; andfiowin t'ne gaseous"medium into and-cut or the reticulated t film-formed structures of each stage joy "Way er the free-flow passages between stages provided by said tubular films toibe posi tiv'ly laterally moved -about with the iatera-ny transported films between the films of each filmformed'structure for providing intimateturbiilent surface contact of the gas with "the surface supported liquid film's thereof.

.3. A m'ethod tor intimately contacting a descen'dmg liquid "with an ascending gaseous or vaporous "medium in a plurality Of intercommunicatingsuperimposed-stageswithout-substantialhydrostatic'head'therebetween, whichmethod comprises distributing the liquid at each stage to form two mutually-spaced horizontally-disposed surface supported films'corinected by surface supported transfer/film's "extending across the space therebetween and through which the liquid is transferred from-a multiplicity of points in the upper film to "a multiplicity of point in the lower film; positively transporting said surface suprorted transfer films in lateraldiretions between said horizontally-disposed films to "cause them to draw liouid from 'anddeliver it to progress'ively-different parts of said upper and lower horizontally disposed films; transferring liouid from the lower film of each stage while maintaming surface support thereof to the upper film of an underlying stage; 'pas'sin'gthegaseous medium upwardly in each-stage in turbulent contact with the l id pass ng downwardly throu h sa d transfer-films and with said horimntal "films: and. rass'in "the aseous medium f eely upwardly from eac 'stagefto an overlying stage.

'4. In the .eonta'ctlng of a descending li 'u d with an ascending gaseous 'or *vaporous medi m, a Tmthod in which the liouid is Spread out at each stage to form two mutually-s aced surface supported horizontally-dispo ed fi ms connected by surface su orted transfer fi-lms posit vely moved about relat veth'ereto in the spaces therebetween, and throughwhich the lim id is transferred from amultinlicity o'f hori' 'o'nt lly-mov ng points in the 'upper'fim to "a multiplicity of o izontally-moving o nts in the lower film, in which the humid is transferred from the lower film of each ,sita e to the u per film of an "underlying stage in the form of surface supported tubular films open to the spaces between the transfer films of said stages'in which 'the'gaseous medium passing upwardly in each stage ismoved between said horizontal "films and brought forcibly into surface 'cont'actwi'th "the "surface supported liquid passing downwardly through said moving transfer films and entending in said "horizontal films, and in which "the gaseous medium passes freeiiy upwardly from each stage to an overlying -stage material upwardly and liquid material down-- wardiy in said "ctilumn, mutually-spaced monzom tal apertured partitions dividing said column into a plurality of superposed cells, drive means associated with said column, and movable distributing elements positioned between said partitions and driven by said drive means, said distributing elements lying in close juxtaposition to said partitions for wiping liquid materials descending in said column over the top and bottom sides of said partitions and over said distributing elements and for producing turbulent surface contact therewith of gaseous materials ascending in said column.

6. A gas and liquid contact device comprising a vertical column with means for flowing gaseous material upwardly and liquid material downwardly in said column, mutually-spaced horizontal apertured partitions dividing said column into a plurality of superposed cells, drive means associated with said column, and spaced spiral distributing elements positioned between said part1- tions and rotated by said drive means, said distributing elements lying in close juxtaposition to said partitions for wiping liquid materials descending in said column over the top and bottom sides of said partitions and over said spaced spiral elements, and for producing turbulent surface contact therewith of gaseous materials ascending in said column.

'7. A contact device according to claim 6, in which said spaced spiral distributing elements are rotated at a suitable speed and in a direction to sweep the gases and liquids inwardly toward the center of rotation counter to the tendency of centrifugal force to move them in the opposite direction.

8. A cell for gas and liquid contact apparatus, comprising a pair of mutually-spacedhorizontal apertured partitions; means for depositing l1qu1d n the upper side of the upper partition and means for supplying gaseous medium to the underside of the lower partition; the apertures in said upper partition being of a size not bridged by the liquid so that the liquid passes therethrough in the form of tubular films; movable distributing means extending between said partitions and movable in close juxtaposition thereto and formed to have only wiping clearance therewith so as to spread the liquid from said tubular films as a top film extending over the underside of said upper partition, to pick up liquid in film form, from a multiplicity of moving points in said top film, and to conduct the liquid down wardly in film form and spread it on the upper side of the lower partition; the distributing means defining gas passages too lar e 0 b bridged by the liquid so that the gas passes freely between the films of liquid supported by the distributing means; the apertures in said lowerpartition being of a size not bridged by the l1qu1d so that the liquid passes therefrom in the form of tubular films; said tubular films plOVldlIlg for the free ingress and egress of gaseous medium to be turbulently contacted with the film-spread liquid in said cell.

9. A cell for gas and liquid contact apparatus, comprisin a pair of mutually-spacedhorizontal apertured partitions; means for deposit ng l1qu1d on the upper side of the upper part1t1on and means for supplying gaseous medium to the underside of the lower partition; the apertures in said upper partition being of a size not bridged by the liquid so that the liquid passes therethrough in the form of tubular films; spaced spiral distributing means extending betweensaid partitions and rotatable in close uxtapos1t on thereto to have only wiping clearance therewith so as to spread the liquid from said tubular films as a top film extending over the underside of said upper partition, to pick up liquid in film form, from a multiplicity of moving points in said top film, and to conduct the liquid downwardly in film form and spread it on the upper side of the lower partition; the spiral distributing means affording gas passages between its turns too large to be bridged by the liquid so that the gas passes freely between the films of liquid supported on the spiral walls thereof; the apertures in said lower partition being of a size not bridged by the liquid so that the liquid passes therefrom in the form of tubular films; said tubular films providing for the free ingress and egress of gaseous medium to be turbulently contacted with the film-spread liquid in said cell.

10. A fractionating apparatus comprising a vertical column with means for flowing gaseous material upwardly and liquid material downwardly in said column, mutually-spaced horizontal apertured partitions dividing said column into a plurality of superposed cells, drive means associated with said column, movable distributing means extending between and in close proximity to said partitions and having only wiping clearance therewith and driven by said drive means for spreading the descending liquid fractions over the top and bottom sides of said partitions and over said distributing means, the distributing means defining gas passages too large to be bridged by the liquid so that the gas passes freely between the films of liquid supported by the distributing means, said apertures being of a size not bridged by said descending liquid, whereby the descending liquid fractions pass through said partitions and cells substantially entirely in moving film form, and whereby the ascending vapors pass through said partitions and cells and are brought into turbulent surface contact with said liquid fractions without having to overcome hydrostatic heads between cells.

11. A gas and liquid contact device comprising a vertical cylindrical column with means for flowing gaseous material upwardly and liquid material downwardly in said column, mutuallyspaced horizontal apertured annular partitions dividing said column into a plurality of superposed cells, a vertical rotatable drive shaft extending centrally of said column, movable distributing elements carried by said shaft and extending between and in close proximity to said partitions and having only wiping clearance therewith and driven by rotation of said shaft for spreading the descending liquid fractions in film form and producing turbulence in the ascending gases, the distributing means defining gas passages too large to be bridged by the liquid so that the gas passes freely between the films of liquid supported by the distributing means, the apertures in said partitions being of a size not bridged by the descending liquid and opening freely from one cell to the next.

12. A contact device according to claim 11, in which the inner edges of the apertured partitions and the adjacent portions of the rotating distributing element and shaft assembly are arranged in substantially sealing relation to each other.

13. A contact device according to claim 11, said shaft carried elements, each comprising a spiral sweep lying between and in closely-spaced liquid spreading relation to the overlying and underlying apertured partitions.

14. A contact device according to claim 13, in which said spiral sweeps are rotated in the direcaccuse tion to sweep the gaseous and liquidphases inwardly toward said shaft counter to their tendency to move outwardly under centrifugal force.

15. In a gas and liquid contact apparatus comprising a column having a vertical cylindrical casing and means for causing gas to ascend the column and liquid to descend the column, the combination with said casing. of a plurality of parallel spaced foraminous plate members extending transversely therein, and means includ ing rotary sweeps one between each pair of plate members, arranged in close, film-spreading, juxtaposition thereto to spread the liquid filmwise on the under side of the upper plate'member, conduct the liquid filmwise between each plate member and the plate member next below it, and spread the liquid filmwise on the upper side of the underlying plate member, said rotary sweeps having gas and liquid passages therethrough not bridged by the liquid, whereby spraying and blowback of the liquid is avoided.

16. A gas and liquid contact device comprising a vertical column with means for supplying liquidto descend therethrough and gas to ascend therethrough, mutually-spaced horizontal apertured partitions dividing said column into a plurality of superposed cells, liquid film-supporting sweep means extending substantially throughout the height of each cell in close film spreading juxtaposition to the upper and lower partitions thereof, and means for producing relative rotation between said film-supporting sweep means and said apertured partitions to spread the descending liquid on the top and bottom surfaces of said partitions and effect continuous cross-mixing thereof, said sweep means havin gas and liquid passages therethrough not bridged by the liquid, whereby spraying and blowback of the liquid is avoided. I

17. A gas and liquid contact device comprising a vertical column with means for supplying liquid to descend therethrough and gas to ascend therethrough, mutually-spaced horizontal apertured partitions dividing said column into a plurality of superposed cells, movable liquid film-support ing and gas-agitating sweep means extending substantially throughout the height of eachcell, and means for moving said filmsup-porting and gas-agitating sweep means relative to said aper tured partitions to positively effect continuous cross-mixing of the descending liquid and positive transverse motion of the liqud films relative to the ascending gases, said sweep means. ly ng in close liquid wiping relation to the overlying and underlying partitions and providing spaced film carrying walls with free gas passages therebetween, whereby spraying and blowback of the liquid is avoided.

18. A method of effecting contact between a descending liquid and an ascending gas which comprises spreading the liquid in upper and lower wall supported apertured horizontal films and transferring the liquid from the upper film to the lower film via wall supported connecting films extending to, and maintained in relative lateral translation with respect to, the upper and lower wall supported films so that said wall supported connecting films are supplied with liquid drawn successively from many different points in said upper horizontal film and deliver liqu d successively to many different points in said lower horizontal film, thereby to effect continuous cross-mixing of the liquid content of the films while maintaining wall support thereof to eliminate blow-back.

19;.A method according to claim 18 further comprising the stepof' maintaining continuously open the apertures in said horizontal .films' and forcing the ascending. gas to pass upwardly through said continuously open. aperturesv and between said connecting films while. maintaining said filmssubstantially intact, wherebyblowback is avoided.

20. A method of contacting a descending liquid with a gaseous or vaporous medium whichconsists inrepeatedly wiping andspreading' the-de scending liquid over relatively movingisurfaces' during the descent thereof in continuously changing moving films havingcontinuously open gas passages therethrough, and passing the gasee ous or vaporous medium. through said gas pass sages upwardly'relative to. the'said moving films in turbulent contact with the surfaces of the surface supported films, whereby channelling and spraying and blowbacl; of liquid are avoided,

21. A method of contacting a: descending liquid with a gaseous or vaporous medium. which consists in repeatedly. wiping. and spreading the descending liquid over relatively movingsurfaces during the. descent thereof in continuously changing moving films of transversely discontinuous form providing free passages there'- through and therebetween unbridged by thefilms, andpassing the gaseous or vaporous medium upwardly through said bridged free passages=relative to the said moving films in turbulent. contact with the surfaces of the. surface supported films, whereby channelling and. spraying and blow'back of liquid are avoided.

22..A method of effecting. contact betweena descending liquid. and an ascending gas. which comprises spreading the liquid in upper. and lower continuously aperturedv horizontal well supported films, and continuously wall support-- ing and transferring liquid film-wise:from.regularly progressively shifting'positions in the upper film to regularly progressively shifting positions in the. lower film, while forcing the ascending gas to pass upwardly through the continuous aper-, tures in said wall supported horizontal films and in surface contact with saidwall supported.-hori-- zont'al films and the wall supported films trans ferring liquid therebetween.

23. A counter'current gas and liquid contact.- apparatus particularly adapted to minimize. blowbacl: and channelling comprising: avertical tower; a plurality of horizontal partitions subdividing the length ofv the tower into cells,

said partitions being provided with apertures:

therethrough of a size. too large to. .be bridged plurality of sweeps each rotatable about a vertical axis and one located in each cell, each sweep being provided with passages extending from its top surface to its bottom surface and of a size too large to be bridged by the liquid so that in operation gas may ascend through the sweep passages as liquid descends filmwise along the walls thereof; each of said sweeps having its top surface juxtaposed closely to the under surface of the partition forming the top of its cell so that as the sweep is rotated the upper edges of its walls will engage with liquid hanging from the under side of the overlying partition and wipe liquid therefrom for flow down said sweep walls to form hanging bodies of liquid at the bottom edges of said sweep walls, and each of said sweeps having its bottom surface juxtaposed closely to the top surface of the partition forming the bottom of its cell so that as the sweep is rotated the liquid suspended from the bottom edges of its walls is smeared or spread over the top surface of the underlying partition; means for supplying gas to the lower reaches of said tower and liquid to the upper reaches thereof for countercurrent flow therein; and means for rotating said sweeps at a slow rate of speed sufficient to cause them to mechanically pick up liquid flowing downwardly through said partitions and hanging from the under sides thereof before the liquid falls therefrom into free suspension in the gas and to thereafter mechanically spread such liquid over the upper sides of the next lower partitions while continuously supporting the liquid by adhesion to the sweep walls during its descent therealong and until it is spread on the underlying partition walls.

24. A countercurrent gas and liquid contact apparatus adapted to minimize blowback and channelling, comprising a vertical tower, two sets of relatively movable elements in the tower, each of said sets comprising a plurality of vertically spaced horizontally disposed elements provided with apertures therethrough of a size too large to be bridged by the liquid so that in operation gas may ascend through said apertures while liquid descends filmwise along the bounding walls of said apertures to hang from the lower faces of the elements, the elements of one of said sets alternating with those of the other, and said alternating elements having their adjacent top and bottom faces closely spaced by distances smaller than the hanging depth of liquid de pending from the under faces of the elements, means for flowing gas upwardly through said elements and liquid downwardly therethrough, and means for producing relative motion between said sets of elements to cause them to continuously mechanically support liquid descending in films therethrough while continuously crossmixing the liquid and gas moving from each element to the next.

25. Gas and liquid contact apparatus according to claim 24, in which the elements of one of said sets are in the form of perforated plates having flat top surfaces so that the liquid flowing thereto from the elements of the other set is spread out filmwise on the flat top surface of said plates to descend filmwise therefrom along the bounding walls of the perforations therethrough.

26. Gas and liquid contact apparatus according to claim 24, in which the elements of one of said sets are in the form of perforated plates having fiat under surfaces so that the liquid flowing thereto along the bounding walls of the perforations therethrough may be spread out filmwise on said flat under surfaces incident to the sweeping of incipient drip therefrom by the elements of the other set.

27. Gas and liquid contact apparatus according to claim 24, in which the elements of one of said sets are in the form of perforated plates having flat top surfaces so that the liquid flowing thereto from the elements of the other set is spread out filmwise on the fiat top surface of said plates to descend filmwise therefrom along the bounding walls of the perforations therethrough, and in which the said perforated plates also have fiat under surfaces so that the liquid flowing thereto along the bounding walls of the perforations therethrough may be spread out filmwise on said flat under surfaces incident to the sweeping of incipient drip therefrom by the elements of the other set.

28. A method of gas and liquid contact that consists in flowing gas upwardly within a column while flowing liquid downwardly filmwise therein, particularly characterized in that the liquid is maintained during its descent in wall supported films spaced to permit free upward passage of the gas therethrough, and in that spaced horizontal portions of the column of ascending as and descending wall supported liquid films are continuously positively transported horizontally between other portions thereof at a rate so related to the liquid flow that essentially wall support of the liquid is continuously maintained notwithstanding that the continuity of individual descending films is continuously being broken and reestablished in new relations whereby the gas and the liquid are continuously cross-mixed to present channelling without any substantial spraying and blowback of the liquid.

AUBREY KEITH BREWER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,292,125 Stevens Jan. 31, 1919 1,650,140 Kuhni Nov. 22, 1927 2,042,127 Sayles May 28, 1936 2,072,382 Robinson Mar. 2, 1937 2,169,338 Ditto Aug. 15, 1939 2,234,921 Webb Mar. 11, 1941 2,317,951 Burk Apr. 27, 1943 2,344,560 Palkin Mar. 21, 1944 2,387,231 Bottoms et al Oct. 23, 1945 2,538,466 Marco Jan. 16, 1951 2,572,049 Oakes Oct. 23, 1951 FOREIGN PATENTS Number Country Date 196,919 Germany Nov. 18, 1905 

